鲁西徂徕山南部花岗闪长斑岩锆石LA-ICP-MS U-Pb定年及其地质意义

LA-ICP-MS U-Pb Dating of the Zircons from Granodiorite-porphyry in Culaishan of Western Shandong and Its Geological Implications

摘要:

出露于鲁西徂徕山南部的花岗闪长斑岩是鲁西中生代岩浆活动的重要记录，在野外地质工作的基础上，通过对其进行锆石LA-ICP-MS U-Pb同位素年代学研究，得到了花岗闪长斑岩的形成时代，并对鲁西地区中生代的岩浆活动进行了讨论。研究得到，谐和度＞90%的锆石中存在~2.5Ga的继承性岩浆锆石和125 ~130Ma的岩浆锆石。经分析，得到其加权平均年龄为（127.3±1.2）Ma（MSWD=1.3），认为这一年龄代表了花岗闪长斑岩的形成年龄，而~2.5Ga的继承性岩浆锆石的存在说明了花岗闪长斑岩的源区可能来自于华北古老基底或在岩浆侵位过程中遭受了古老基底的混染作用。

Abstract:

Granodiorite-porphyry in Culaishan of Western Shandong is one of the most important record of Mesozoic magmatism. On the basis of lithology, the forming age of granodiorite-porphyry have been gained, and Mesozoic magmatism in western Shandong has been discussed. It is found that there are inherited magma with the age of ~2.5 Ga and magmatic zircon with the age of 125~130Ma in the zircon with the consonant degree is over than 90%. The weighted average age is (127.3 + 1.2) Ma (MSWD=1.3). It is regarded that this age represents the formation age of granodiorite porphyry, and the existence of the inherited magmatic zircon of ~2.5Ga indicates that the source area of the granite diorite may come from the ancient base of Northern China or experience the contamination in the process of magma emplacement.